Optical system

Abstract

Optical systems including first and second optical stacks and adapted to provide an adjustable dioptric correction are described. The first optical stack includes a first optical lens and a partial reflector. The second optical stack is convex along orthogonal first and second axes and includes a second optical lens and a reflective polarizer. The reflective polarizer has at least one first location having a radial distance r 1 from an optical axis of the second optical stack and a displacement s 1 from a plane perpendicular to the optical axis at an apex of the reflective polarizer, where s 1 /r 1 is at least 0.1. A quarter wave retarder is disposed between the second optical stack and the first optical stack.

What is claimed is: 
     
       1. An optical system, comprising:
 a partial reflector having an average optical reflectance of at least 30 % in a desired plurality of wavelengths; 
 a reflective polarizer curved about two orthogonal axes and substantially transmitting light having a first polarization state and substantially reflecting light having an orthogonal second polarization state, at least one location on the reflective polarizer having a radial distance r 1  from an optical axis passing through an apex of the reflective polarizer and a displacement s 1  from a plane perpendicular to the optical axis at the apex of the reflective polarizer, s 1 /r 1  being at least 0.1; and 
 a first quarter wave retarder disposed between the partial reflector and the reflective polarizer, wherein the optical system is adapted to provide an adjustable dioptric correction. 
 
     
     
       2. The optical system of  claim 1 , wherein the adjustable dioptric correction is provided, at least in part, by an adjustable distance between the partial reflector and the reflective polarizer. 
     
     
       3. The optical system of  claim 1 , wherein a first optical stack comprises the partial reflector, and the adjustable dioptric correction is provided, at least in part, by an adjustable shape of the first optical stack. 
     
     
       4. The optical system of  claim 1 , wherein a second optical stack comprises the reflective polarizer, and the adjustable dioptric correction is provided, at least in part, by an adjustable shape of the second optical stack. 
     
     
       5. The optical system of  claim 1 , wherein the reflective polarizer comprises at least one layer substantially optically biaxial at at least one first location on the at least one layer away from the optical axis and substantially optically uniaxial at at least one second location away from the optical axis. 
     
     
       6. The optical system of  claim 1 , wherein the reflective polarizer is a wire grid polarizer. 
     
     
       7. The optical system of  claim 1 , further comprising an image surface and a stop surface, the partial reflector disposed between the image surface and the stop surface, the reflective polarizer disposed between the partial reflector and the stop surface, the reflective polarizer being convex toward the image surface about the two orthogonal axes. 
     
     
       8. The optical system of  claim 1 , further comprising an image surface and a stop surface, the partial reflector disposed between the image surface and the stop surface, the reflective polarizer disposed between the partial reflector and the stop surface, wherein the optical system is adapted to incorporate a prescription lens disposed between the image surface and the partial reflector or between the stop surface and the reflective polarizer. 
     
     
       9. A head-mounted display comprising a first optical system according to  claim 1  and a second optical system according to  claim 1  disposed adjacent the first optical system. 
     
     
       10. An optical system, comprising:
 a partial reflector having an average optical reflectance of at least  30 % in a desired plurality of wavelengths; and 
 a reflective polarizer curved about two orthogonal axes and substantially transmitting light having a first polarization state and substantially reflecting light having an orthogonal second polarization state; and 
 a first quarter wave retarder disposed between the partial reflector and the reflective polarizer, wherein the optical system is adapted to provide an adjustable distance between the partial reflector and the reflective polarizer. 
 
     
     
       11. The optical system of  claim 10 , wherein the optical system is adapted to reduce vergence-accommodation mismatch by adjusting the adjustable distance. 
     
     
       12. The optical system of  claim 10 , wherein the optical system is adapted to provide an adjustable dioptric correction, the adjustable dioptric correction being provided, at least in part, by the adjustable distance between the partial reflector and the reflective polarizer. 
     
     
       13. The optical system of  claim 10 , wherein the reflective polarizer comprises at least one layer substantially optically biaxial at at least one first location on the at least one layer away from an optical axis passing through an apex of the reflective polarizer and substantially optically uniaxial at at least one second location away from the optical axis. 
     
     
       14. The optical system of  claim 10 , wherein the reflective polarizer is a wire grid polarizer. 
     
     
       15. The optical system of  claim 10 , further comprising an image surface and a stop surface, the partial reflector disposed between the image surface and the stop surface, the reflective polarizer disposed between the partial reflector and the stop surface, wherein the optical system is adapted to incorporate a prescription lens disposed between the image surface and the partial reflector or between the stop surface and the reflective polarizer. 
     
     
       16. A head-mounted display comprising a first optical system according to  claim 10  and a second optical system according to  claim 10  disposed adjacent the first optical system. 
     
     
       17. A head-mounted display comprising:
 a first optical system comprising:
 a first image surface; 
 a first exit pupil; 
 a first reflective polarizer disposed between the first exit pupil and the first image surface, the first reflective polarizer convex about two orthogonal axes; 
 a first partial reflector disposed between the first reflective polarizer and the first image surface, the first partial reflector having an average optical reflectance of at least 30% in a pre-determined plurality of wavelengths; and 
 a first quarter wave retarder disposed between the first reflective polarizer and the first partial reflector; and 
 
 a second optical system disposed proximate the first optical system, the second optical system comprising:
 a second image surface; 
 a second exit pupil; 
 a second reflective polarizer disposed between the second exit pupil and the second image surface, the second reflective polarizer convex about two orthogonal axes; 
 a second partial reflector disposed between the second reflective polarizer and the second image surface, the second partial reflector having an average optical reflectance of at least 30% in the pre-determined plurality of wavelengths; and 
 a second quarter wave retarder disposed between the second reflective polarizer and the second partial reflector, 
 
 wherein a first distance between the first reflective polarizer and the first partial reflector is adjustable, and a second distance between the second reflective polarizer and the second partial reflector is adjustable. 
 
     
     
       18. The head-mounted display of  claim 17  being adapted to reduce vergence-accommodation mismatch by electronically adjusting the first and second distances. 
     
     
       19. The head-mounted display of  claim 17  being adapted to provide an adjustable dioptric correction, the adjustable dioptric correction being provided, at least in part, by the adjustable first and second distances. 
     
     
       20. The head-mounted display of  claim 17  further comprising an eye-tracking system, the head-mounted display being adapted to adjust the first and second distances in response to signals received from the eye-tracking system.